25 years after the cleansing of the Capitol Wasteland the Brotherhood of Steel discovers the location of Vault 46, a veritable treasure trove. A sealed chamber within holds an automated factory facility capable of turning out high tech weapons and gear. A party of Vault Dwellers and Brotherhood troops travels to Montana to open Vault 46 only to find it overrun with ghouls and mutants, who are unaware of the greater treasure that lies within.